London, Sept 8 : Can't stop eating junk food while watching TV? You may think it may be because you like the taste, but it's not the case.

It is because we are such creatures of habit that once we have associated a place with a certain kind of food, like popcorn at the cinema, we will keep eating it - even if it''s stale, scientists say.

Researchers from the University of Southern California devised a test to see what causes us to overeat.

They gave people about to enter a cinema a bucket of just-popped fresh popcorn, or stale week-old popcorn.

Moviegoers who didn't usually eat popcorn at the movies ate much less stale popcorn than fresh popcorn because it just didn''t taste good.

But those who said they typically had popcorn at the movies ate about the same amount of popcorn whether it was fresh or stale.

In other words, for those in the habit of snacking at the movies, it made no difference whether the popcorn tasted good or not.

"When we've repeatedly eaten a particular food in a particular environment, our brain comes to associate the food with that environment and makes us keep eating as long as those environmental cues are present," the Daily Mail quoted lead author David Neal as saying.

"The results show just how powerful our environment can be in triggering unhealthy behaviour," Mr Neal said.

''Sometimes willpower and good intentions are not enough, and we need to trick our brains by controlling the environment instead," he added.

The study has been published in the journal Personality and Social Psychology Bulletin. (ANI)